Bistable switching device



Dec. 13, 1966 BERGSTRASSER 3,292,121

BISTABLE SWITCHING DEVICE Filed Nov. 2, 1964 W AM. I

United States Patent ()fi 3,292,121 Patented Dec. 13, 1966 ice 3,292,121 BISTABLE SWITCHING DEVICE .Georg Bergstrfisser, Frankfurt am Main, Germany, as-

signor to Telefonbau und N ormalzeit G.m.b.H., Frankfurt am Main, Germany Filed Nov. 2, 1964, Ser. No. 408,174 Claims priority, applic%tit2)g glermany, Nov. 22, 1963,

2 Claims. Cl. 335-153 This invention relates to bistable electromagnetic switches, and more particularly to bistable reed switches as widely used in communication engineering.

It is a general object of this invention to provide improved bistable elec'tromagnetic switches.

Another object of this invention is to provide bistable electromagneticswitches, in particular bistable electromagnetic reed switches, not prone to faults or accidental operation.

Another object of this invention is to provide reed switches of the kind disclosed and claimed in United States Patent 3,067,304 to G. Bergstrasser et al., issued December 4, 1962 for Switching Contacts Controlled by MagneticFields which are bistable and not prone to faulty or accidental operation.

' The contacts of electromagnetic reed switches are nor- 'mally open and are being closed by the action of an electromagnet. The reeds of bistable reed switches are also under the action of a fixed permanent magnet. The field action of that permanent magnet is not sufficiently strong to cause engagement of the cooperating contacts of the reed switch, but is sufficiently strong to maintain the contacts of the reed switch in the closed position, or engaged position, upon having been moved to that position by the action of the aforementioned energizing electromagnet. Hence the contacts remain closed, or engaged, upon deenergization of the energizing electromagnet. Opening of the contacts is effected by energizing the aforementioned electromagnet in reverse, or inverting the direction of the magnetic field thereof.

In bistable prior art reed switches of this description the magnetic bias of a movable contact by a fixed perma- 'nent magnet is not sufiicient to cause engagement of the contacts. Because of the presence of this bias the contacts may be moved into engagement by relatively small electric impulses other than the normal operating impulse.

In other words, prior art bistable reed switches including an operating electromagnet and a permanent magnet for maintaining the contacts closed, once closed by the action of the operating electromagnet, are prone to faulty or accidental operation.

It is, therefore, another object of this invention to provide bistable electromagnetic reed switches including an operating electromagnet and a permanent magnet for maintaining contacts closed, once closed by the action of the operating electromagnet, which reed switches are not subject to faulty or accidental operation on account of the aforementioned magnetic closing bias of one of the contacts or reeds thereof.

According to this invention bistable electromagnetic switches are provided with additional means for varying one of the contacts of the switch against the bias to which the armature is subjected. The armature may be an integral part of one of the contacts of the switch, or an integral part of one contact-supporting reed, in which case the armature will be subjected to the same bias as the contact or reed of which it forms an integral part.

The drawingsillustrate a preferred embodiment of the invention wherein the armature used to vary the reluctance of the path of the flux of the contact-operating electromagnet is formed by a reed of magnetizable material having an edge which forms a contact surface of the switch.

In the drawings FIG. 1 is a diagrammatic representation of a bistable reed switch including a permanent magnet to maintain one of the contacts in the closed position thereof, but not including any means for preventing faulty or accidental operation of the switch;

FIG. 2 shows the same switch as shown in FIG. 1 with means added to vary the reluctance of the path of the flux of an electromagnetic contact operating coil, the contacts of the switch being shown in the open position, or disengaged position, thereof; and

FIG. 3 shows the same structure as FIG. 2 with the contacts thereof in their closed position, or engaged position.

Referring now to FIG. 1 'of the drawing, numeral 1 has been applied to indicate an elongated envelope of glass, or other insulating material. Arranged at the right side of envelope 1 is a flat current-carrying leaf spring or lamination 2 of a magnetizable material. Leaf spring or lamination 2 extends in a direction longitudinally of envelope or housing 1 and projects transversely through the wall thereof from the outside of envelope 1 into its inside. At the point where leaf spring or lamination 2 projects through the wall of envelope 1 the latter forms a gas-tight seal. A current-carrying leaf spring or lamination 3, 4 is arranged at the left side of envelope or housing 1 in a similar fashion as leaf spring or lamination 2. Both leaf springs or laminations 2 and 3, 4 are arranged in sub- .stantially the same plane, each forming at the edge portion thereof a pair of juxtaposed normally spaced or open contact surfaces. The left leaf spring or lamination 3, 4 includes a length of reduced cross-section which is substantially sinusoidally shaped, forming a bridge or interconnection between the left portion 3 of the left leaf spring 3, 4 and the right portion 4 thereof. This geometry imparts to leaf spring 3, 4 a freedom of relative motion of its parts 3, 4 in the common plane defined by leaf springs 2 and 3, 4. The juxtaposed ends of laminations 2 and 3, 4 define normally a gap 5 therebetween. Reference numeral 6 has been applied to indicate a contact operating winding or coil mounted on envelope or housing 1 for establishing the magnetic field required to move the axially inner end 4 of leaf spring 3,4 relative to lamination 2. The flux established by winding or coil 6 extends through lamination 2 and across gap 5 and through portion 4 of lamination 3, 4. Preferably additional magnetizable means (not shown) are provided to complete the path of the flux of winding or coil 6 in such a fashion as to minimize the reluctance thereof. If magnet winding or coil 6 is sufficiently energized portion 4 of leaf spring or lamination 3, 4 moves relative to portion 3 thereof and the contact-surface-forming edges of parts 4 and 2 are caused to engage, thus closing an electric circuit.

Reference numeral 7 has been applied to indicate a permanent magnet arranged outside of envelope 1 immediately adjacent to the gap formed between the juxtaposed edges of parts 2 and 4. The action of this magnet keeps parts 2 and 4 in physical engagement subsequent .to deenergization of electromagnet coil 6, thus maintaining the circuit closed that had been closed by the action of electromagnet coil 6.

'pulse. avoidable in any communication system, the reduction Without the presence of permanent magnet 7 the axially inner portion 4 of leaf spring 3, 4 assumes the position shown in FIG. 1 by dotted lines. Under the bias of permanent magnet 7 the portion 4 of leaf spring 3, 4 moves to the position shown in FIG. 1 in solid lines. This results in a reduction of the width of the gap formed between the juxtaposed narrow contact-surface-forming edges of parts 4 and 2. As a result of such reduction of the width of gap 5, there is a danger of unintentional closing of the circuit by an unintentional engagement of parts 4 and 2, as may be caused by a relatively slight energization of .winding or coil 6 rather than a normal contact-closing Since relatively weak or noisepulses are hardly of the width of gap 5 by the action of magnet 7 tends to cause malfunctioning of bistable reed switches.

' The structure shown in FIGS. 2 and 3 is not susceptible to malfunctioning. In FIGS. 2 and 3 the same reference characters as in FIG. 1 with a prime added have been applied to indicate like parts. Thus reference character 1' has been applied to indicate an envelope, preferably of glass, housing the axially inner ends of a pair of magnetizable laminations 2' and 3', 4' defining a gap 5 between the juxtaposed narrow contact-surface-forming edges thereof. Housing 1 supports the operating winding 6' for the contact end 4 of leaf spring 3', '4' and permanent magnet 7" maintains part 4 in the closed position upon having been moved to that position by-the action of magnet coil 6'.

The structure of FIGS. 2 and 3 further includes a permanent magnet 8 arranged outside of envelope 1' adjacent to the gap 5 formed between parts 4 and 2'. Envelope 1' is preferably rectangular in cross-section and comprises two relatively wide sides extending parallel to the plane defined by laminations 2 and 3', 4' and two relatively narrow sides extending at right angles to the aforementioned plane. Permanent magnets 7' and 8' are arranged outside of envelope 1' in juxtaposed position to the aforementioned narrow sides thereof. The magnetic field established by permanent magnet 8' tends to increase the width of gap 5', i.e. the action of permanent magnet 8' is opposed to the action of permanent magnet 7'. In other words, the magnetic field established by permanent magnet 8 weakens the magnetic field established by permanent magnet 7. Therefore a relatively strong impulse is required to energize coil or winding 6' to the extent required to cause engagement of parts 2' and 4' under the action of the magnetic field produced by coil or winding 6'. Thus the danger of faulty operation of the reed switch is eliminated by the presence of additional permanent magnet 8 and its action upon part 4 operating as an armature for varying the reluctance of the path of the fiux established by coil or winding 6'.

When the portion 4' of leaf spring 3, 4 is sufliciently attracted by the action of the magnetic field established by winding or coil 6 to move toward part 2' and to reduce the width of gap 5', the action of permanent magnet 8' on portion 4' decreases progressively as the distance between portion 4' and permanent magnet 8' increases. As a result of the aforementioned movement of part 4', the action of permanent magnet 7' upon part 4 becomes preponderant and permanent magnet 7 holds the latter part firmly in engagement with lamination 2', once such physical engagement has been established.

In order to separate part 4 from lamination 2' coil or winding 6' is energized in the opposite direction to such an extent as to overcome the magnetic action of permanent magnet 7 upon part 4'.

It will be apparent from the foregoing that the longitudinal axes of both bar magnets 7 and 8' are arranged :surfaces spaced substantially equidistantly from reeds or laminations 2' and 3', 4. As a result of this arrange- 4 ment the spacing between the poles of the two permanent bar magnetc 7", 8", and of reeds or laminations 2 and 3, 4' is relatively small and the entire flux path of permanent bar magnets 7, 8' is extremely compact.

It is possible to stack units of the kind shown in FIGS. 2 and 3 and to provide a common operating magnet for the constituent units of such a stack. Such a stack may be provided with a common permanent magnet for fnain= taining the contacts of the constituent switches thereof in the closed position upon having been moved to that position by the action of the aforementioned common operating magnet. Such a stack may also be provided with an additional common permanent magnet for providing a progressively decreasing magnetic bias for the movable contacts of the stacked reed switches.

. It will be apparent from the foregoing that magnet .8 is a contact closing threshold establishing means, and

-magnet 7 a latching means, and that poles of opposite polarity of magnets 7, 8 are arranged along a line at right angles to the longitudinal axes of envelope 1.

While, in accordance with the patent statutes, I have disclosed the specific details of a preferred embodiment of my invention, it is to be understood that the details are merely illustrative and that many variations thereof may be made without departing from the spirit and scope of the invention. It is my desire, therefore, that the language of the accompanying claims be interpreted as broadly as possible and limited only by the prior state of the art.

I claim as my invention:

1. A bistable reed switch comprising in combination:

(a) an elongated housing having a housing wall of in sulating material including end portions and lateral portions;

(b) a first reed defining a predetermined plane and projecting from the outside of said housing transversely across one of said end portions of said housing into the inside of said housing and having a first contact surface formed by an edge of said first reed adjacent the axially inner end thereof;

(0) a second reed of magnetizable material projecting at a predetermined point thereof from the outside of said housing transversely across the other of said end' portions of said housing into the inside of said housing, said second reed being arranged in the plane defined by said first reed, said second reed having a second contact surface formed by an edge of said second reed adjacent the axially inner end thereof juxtaposed to said first contact surface of said first reed, said second reed further having a portion of reduced cross-sectional area situated inside said housing between said predetermined point thereof and said second contact surface, said portion of reduced cross-sectional area imparting to said second contact surface of said second reed a freedom of motion within said plane defined by said first reed relative to said predetermined point of said second reed and relative to said first contact surface of said first reed, said first contact surface of said first reed and said second contact surface of said second reed defining a gap of predetermined width in the absence of magnetic forces acting upon said second reed;

(d) a first permanent fixed bar magnet arranged adjacent said gap and adjacent the longitudinal edges of said first reed and of said second reed substantially parallel to said first reed and to said second reed and having a pair of end surfaces spaced substantially equidistantly from said first reed and from said second reed, said first bar magnet establishing a magnetic field tending to reduce said predetermined width of said gap between said first contact surface of said first reed and said second contact surface of said second reed and to maintain said first contact surface of said first reed and said second contact surface of said. secondreed in abutting engagement upon any abutting engagement thereof caused by electromag netic action;

(e) electromagnetic winding means mounted upon said housing for establishing a magnetic field to cause abutting engagement of said first contact surface of said first reed by said second contact surface of said second reed; and

(f) a second permanent fixed bar magnet arranged adjacent said gap and adjacent the longitudinal edges of said first reed and of said second reed substantially parallel to said first reed and said second reed, said second magnet having a pair of end surfaces spaced substantially equidistantly from said first reed and from said second reed, said second bar magnet being arranged to establish a magnetic field tending to bias the axially inner end of said second reed away from the axially inner end of said first reed and to increase the width of said gap between said first contact surface of said first reed and said second contact surface of said second reed.

2. A bistable reed switch comprising in combination:

(a) an elongated envelope of glass substantially rectangular in cross-section having a pair of juxtaposed relatively wide sides and a pair of juxtaposed relatively narrow sides;

(b) a pair of spaced current-carrying laminations of a magnetizable material arranged substantially in a common plane, each of said pair of laminations having one end arranged outside said envelope and projecting through the wall of said envelope into the inside thereof, one of said pair of laminations including a length of reduced cross-sectional area imparting to portions thereof a freedom of relative motion within said common plane, edges of said pair of laminations inside said envelope forming a pair of cooperating normally spaced contact surfaces arranged in a predetermined slanting relation relative to the longitudinal axis of said envelope;

(c) an electromagnet winding mounted on said envelope establishing a magnetic flux through said pair of laminations across said contact-surface-forming edges thereof to cause closing of said contact surfaces; and

(d) a pair of permanent fixed bar magnets arranged substantially parallel to said pair of relatively narrow sides of said envelope each adjacent an opposite of said pair of narrow sides of said envelope, each of said pair of magnets having a pole of opposite polarity arranged along a line at right angles to the longitudinal axis of said envelope, one of said pair of magnets being arranged to establish a magnetic field tending to maintain said contact surfaces closed upon closing thereof under the action of said electromagnet winding, and the other of said pair of magnets being arranged to establish a magnetic bias tending to oppose the closing action of said electromagnet winding.

References Cited by the Examiner UNITED STATES PATENTS 10/1962 Peek 200-87 11/ 1965 Matthias 20087 OTHER REFERENCES Hatzinger, Germany, application Serial No. 1,134,762,

April 16, 1962.

BERNARD A. GILHEANY, Primary Examiner.

I. BAKER, Assistant Examiner. 

1. A BISTABLE REED SWITCH COMPRISING IN COMBINATION: (A) AN ELONGATED HOUSING HAVING A HOUSING WALL OF INSULATING MATERIAL INCLUDING END PORTIONS AND LATERAL PORTIONS; (B) A FIRST RED DEFINING A PREDETERMINED PLANE AND PROJECTING FROM THE OUTSIDE OF SAID HOUSING TRANSVERSELY ACROSS ONE OF SAID END PORTIONS OF SAID HOUSING INTO THE INSIDE OF SAID HOUSING AND HAVING A FIRST CONTACT SURFACE FORMED BY AN EDGE OF SAID FIRST REED ADJACENT THE AXIALLY INNER END THEREOF; (C) A SECOND REED OF MAGNETIZABLE MATERIAL PROJECTING AT A PREDETERMINED POINT THEREOF FROM THE OUTSIDE OF SAID HOUSING TRANSVERSELY ACROSS THE OTHER OF SAID END PORTIONS OF SAID HOUSING INTO THE INSIDE OF SAID HOUSING, SAID SECOND REED BEING ARRANGED IN THE PLANE DEFINED BY SAID FIRST REED, SAID SECOND REED HAVING A SECOND CONTACT SURFACE FORMED BY AN EDGE OF SAID SECOND REED ADJACENT THE AXIALLY INNER END THEREOF JUXTAPOSED TO SAID FIRST CONTACT SURFACE OF SAID FIRST REED, SAID SECOND REED FURTHER HAVING A PORTION OF REDUCED CROSS-SECTIONAL AREA SITUATED INSIDE SAID HOUSING BETWEEN SAID PREDETERMINED POINT THEREOF AND SAID SECOND CONTACT SURFACE, SAID PORTION OF REDUCED CROSS-SECTIONAL AREA IMPARTING TO SAID SECOND CONTACT SURFACE OF SAID SECOND REED A FREEDOM OF MOTION WITHIN SAID PLANE DEFINED BY SAID FIRST REED RELATIVE TO SAID PREDETERMINED POINT OF SAID SECOND REED AND RELATIVE TO SAID FIRST CONTACT SURFACE OF SAID FIRST REED, SAID FIRST CONTACT SURFACE OF SAID FIRST REED AND SAID SECOND CONTACT SURFACE OF SAID SECOND REED DEFINING A GAP OF PREDETERMINED WIDTH IN THE ABSENCE OF MAGNETIC FORCES ACTING UPON SAID SECOND REED; (D) A FIRST PERMANENT FIXED BAR MAGNET ARRANGED ADJACENT SAID GAP AND ADJACENT THE LONGITUDINAL EDGES OF SAID FIRST REED AND OF SAID SECOND REED SUBSTANTIALLY PARALLEL TO SAID FIRST REED AND TO SAID SECOND REED AND HAVING A PAIR OF END SURFACES SPACED SUBSTANTIALLY EQUIDISTANTLY FROM SAID FIRST REED AND FROM SAID SECOND REED, SAID FIRST BAR MAGNET ESTABLISHING A MAGNETIC FIELD TENDING TO REDUCE SAID PREDETERMINED WIDTH OF SAID GAP BETWEEN SAID FIRST CONTACT SURFACE OF SAID FIRST REED AND SAID SECOND CONTACT SURFACE OF SAID SECOND REED AND TO MAINTAIN SAID FIRST CONTACT SURFACE OF SAID FIRST REED AND SAID SECOND CONTACT SURFACE OF SAID SECOND REED IN ABUTTING ENGAGEMENT UPON ANY ABUTTING ENGAGEMENT THEREOF CAUSED BY ELECTROMAGNETIC ACTION; (E) ELECTROMAGNETIC WINDING MEANS MOUNTED UPON SAID HOUSING FOR ESTABLISHING A MAGNETIC FIELD TO CAUSE ABUTTING ENGAGEMENT OF SAID FIRST CONTACT SURFACE OF SAID FIRST REED BY SAID SECOND CONTACT SURFACE OF SAID SECOND REED; AND (F) A SECOND PERMANENT FIXED BAR MAGNET ARRANGED ADJACENT SAID GAP AND ADJACENT THE LONGITUDINAL EDGES OF SAID FIRST REED AND OF SAID SECOND REED SUBSTANTIALLY PARALLEL TO SAID FIRST REED AND SAID SECOND REED, SAID SECOND MAGNET HAVING A PAIR OF END SURFACES SPACED SUBSTANTIALLY EQUIDISTANTLY FROM SAID FIRST REED AND FROM SAID SECOND REED, SAID SECOND BAR MAGNET BEING ARRANGED TO ESTABLISH A MAGNETIC FIELD TENDING TO BIAS THE AXIALLY INNER END OF SAID SECOND REED AWAY FROM THE AXIALLY INNER END OF SAID FIRST REED AND TO INCREASE THE WIDTH OF SAID GAP BETWEEN SAID FIRST CONTACT SURFACE OF SAID FIRST REED AND SAID SECOND CONTACT SURFACE OF SAID SECOND REED. 